Current understanding of glucose transporter 4 expression and functional mechanisms

Table 6 Recent studies of glucose transporter 4 expression and translocation in the brain

Methods	Materials	Comparisons	Conclusions	Ref.
Western blot.	Brain, skeletal muscle, heart, and whiteadipose tissue from mice. Anti-GLUT4 from Chemicon (1:1000).	Samples from wild type and knockout mice.	Deletion of Slc2a4 in the brain leads to insulin resistance, glucose intolerance, and impaired glucose sensing in the VMH.	[154]
Western blot,Real time-PCR,Immunofluorescence.	Cortex, hypothalamus, cerebella samples from CD-1 mice. Monoclonal anti Glut4 (1F8) from Dr. Paul Pilch, Polyclonal anti Glut4 MC2A from Dr. Giulia Baldini, Polyclonal anti Glut4 αG4 from Dr. Samuel Cushman, Polyclonal anti Glut4 (C-20) from Santa Cruz Biotechnology.	Expression profile in the mouse and rat brain samples.	Slc2a4 mRNA is expressed in cultured neurons. GLUT4 protein is highly expressed in the granular layer of the mouse cerebellum. GLUT4 translocation to the plasma membrane can be stimulated by physical activity.	[155]
Western blot.	Brian tissue from STZ-induced diabetic male Sprague-Dawley rats.Anti-GLUT4 from Millipore (1:1000).	Comparing treatment samples using β-actin and NA/K ATPase as loading controls in Western blot.	Chronic infusion of insulin into the VMH in poorly controlled diabetes is sufficient to normalize the sympathoadrenal response to hypoglycemia via restoration of GLUT4 expression.	[156]
Immunocytochemistry.	Cerebellum and hippocampus from male Sprague-Dawley rats.Rabbit anti-GLUT4 antibody from Alomone Labs (AGT-024, RRID: AB_2631197).	Identifying expression profile and translocation.	GLUT4 is expressed in neurons including nerve terminals.Exercising axons rely on translocation of GLUT4 to the cell membrane for metabolic homeostasis.	[157]
Real-time PCR, Immunocytochemistry.	Cerebral cortex, hippocampus, thalamus, cerebellum, medulla oblongata, cervical spinal cord, biceps muscles from male Wistar rats. Unknown source of antibody.	Identifying expression profile using β -actin as loading control in real-time PCR.	Slc2a4 mRNA is detected in many neurons located in brain and spinal cord. GLUT4 protein is detected in different regions of the CNS including certain allocortical regions, temporal lobe, hippocampus, and substantia nigra.	[158]
Immunocytochemistry, Western blot.	Brain, spleen, kidney from Lrrk2 knockout mice.Anti GLUT4 Avivasysbio (ARP43785_P050, 1:100), andanti GLUT4 from R&D Systems (MAB1262, 1:1000).	Samples from wild type and knockout mice, andanti-β-Tubulin as loading control.	Phosphorylation of Rab10 by LRRK2 is necessary for GLUT4 translocation.Lrrk2 deficiency increases GLUT4 expression on the cell surface in “aged” cells.	[159]
Western blot, Immunofluorescence, real-time PCR.	Brain from Cyp27Tg mice. Anti GLUT4 from Cell Signaling Technology (#2213,1:1000 dilution).	Mice with different treatments.	A reduction of GLUT4 protein expression in brain occurs after 27-OH cholesterol treatment.	[160]
Immunohistochemistry.	Brain, hypothalamus, and other tissues from Sprague–Dawley rats.Anti-GLUT4 antibody from Santa Cruz Biochemicals (1:200), Anti GLUT4 from S. Cushman (1:1000).	Identifying the expression profiles. Soleus muscle as GLUT4 positive control. Antibodies after pre-absorption with the corresponding synthetic peptide were used as negative control. for GLUT4 antibody.	GLUT4 is localized to the micro vessels comprising the blood brain barrier of the rat VMH.GLUT4 is co-expressed with both GLUT1 and zonula occludens-1 on the endothelial cells of these capillaries.	[161]
Electrophysiological analyses, fluorescent microscope.	Brain from GLUT4-EYFP transgenic mice. Fusion protein.	Comparing samples from treatments. A scrambled RNA expressed by AAV acted as a negative control.	GLUT4 neurons are responsible for glucose sensing.	[162]
Western blot,Immunohistochemistry.	Brain samples from 7, 11, 15, 21 and 60 d old Balb/c mice. Rabbit anti-rat GLUT4 from an unknow source (1:2500 dilution for Western and 1:2000 for immunohistochemistry).	Determine the expression profiles. Vinculin is used as the loading control in Western blot.	GLUT4 is expressed in neurons of the postnatal mouse brain. GLUT4 and GLUT8 may mediate the effects of insulin, or insulin-like growth factor on regulations of cognition, memory, behavior, motor activity and seizures.	[163]

AAV: Adeno-associated virus; CNS: Central nervous system; CRR: Counterregulatory response; EYFP: Enhanced Yellow Fluorescent Protein; LRRK2: Leucine-rich repeat kinase 2; STZ: Streptozotocin; VMH: Ventromedial hypothalamus.